IRON-OXIDE PILLARED CLAY WITH LARGE GALLERY HEIGHT - SYNTHESIS AND PROPERTIES AS A FISCHER-TROPSCH CATALYST

New iron oxide pillared montmorillonites have been prepared by the reaction of Na+ montmorillonite with base-hydrolyzed solutions of Fe3+ salts and subsequent thermal conversion of the intercalated polycations. Depending on the hydrolysis conditions used to generate the pillaring solutions, pillared products with basal spacings in the range 18 to 25 Å were obtained. Under optimum hydrolysis conditions (base/metal = 2.0 meq/mol, aging time = 23-147 hr) the pillared products contained 6.8-9.8 Fe3+ ions per O20(OH)4 unit cell and exhibited basal spacings of 25-29 Å. These latter spacings corresponded to exceptionally large gallery heights of 15-19 Å. Upon calcination at 300°C, the spacings decreased to 23-27 Å. N2 BET surface areas after outgassing at 350°C were in the range 270 to 350 m2/g. The pillared products are active catalysts that have undergone Fischer-Tropsch synthesis of hydrocarbons at 275°C and 120-psi (CO: H2 = 1 : 2). The hydrocarbon distribution in the C1-C6 range (1.3% conversion) followed Anderson-Schulz-Flory statistics with a chain propagation probability of α = 0.49. X-ray energy dispersive analysis indicated that substantial amounts of the intercalated iron migrated to the edge sites of the clay particles under reaction conditions. The redistribution of iron resulted in a distribution of gallery heights sufficiently heterogeneous to preclude Bragg X-ray scattering along the 001 direction. Iron migration also occurred upon exposure of the pillared products to the ambient atmosphere for prolonged periods (≥3 months). © 1991.